Headphone Amplifier

This is a handmade headphone amplifier.

〇 Features
・ Maximum amplification factor is 1.5x.
・ Volume is adjusted by switching resistors with a rotary switch.
・ Good channel separation allows for clear listening of even subtle sounds.
・ Powered by USB-C.
・ GND and power are separated for each channel.
・ The output stage uses a non-feedback circuit.
・ No battery is included.
・ USB is for power only and does not have DAC functionality.

There are two rotary switches: one for coarse adjustment and one for fine adjustment. By using them in combination, you can adjust the volume in 36 steps.
*Sound will still be output even when the volume is turned all the way down.

Specifications
〇 Method
・ Unbalanced
〇 Case Size
Case made with a 3D printer (Material: PETG)
W 114mm
H 38mm
D 132mm (154mm including terminals)
〇 Input
・ RCA
〇 Output
・ 4.4mm 5-pole
〇 Power Supply
・ USB-C 5V 1A or higher
〇 Power Consumption
・ 3.6W
〇 Accessories
・ USB cable
〇 Front Panel Layout
Left: Fine volume adjustment (6-step rotary switch)
2: Power switch
3: 4.4mm 5-pole (Output)
4: Spare switch (can be used for gain adjustment, input expansion, etc.)
Right: Coarse volume adjustment (6-step rotary switch)
〇 Rear Panel Layout
・ USB-C terminal
〇 Components Used
・ First stage amplification: OPA627
・ Signal processing: OPA827
・ Output stage: Transistor non-feedback
・ Resistors: DALE metal film, etc.
・ Capacitors: Solid electrolytic capacitors, Nichicon KZ, FG, etc.
〇 Notes
1. The operational amplifier is soldered to the board and cannot be replaced.
2. Please do not modify the unit. We do not offer warranty for defects that occur after modification.
3. In case of malfunction, we will repair it free of charge within one month of purchase.

Please contact us if you have any questions or requests.
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